The present invention relates to an optical alignment tool which can replace the mechanical alignment tools presently being used during the robot teaching process. The optical alignment tool (sensor) consists of a light projector and camera which can be mounted on the robot end effector.
A circular pattern of light, when projected at an angle with respect to a camera axis, which intersects a flat surface, appears as an ellipse to the camera. Since the projected circle radius as well as camera/projector angles are known, the ellipse major and minor axes are known for any given surface angle relative to the sensor. When viewed on a monitor the ellipse dimensions may be used to indicate orientation of the robot end effector with respect to the object. The distortion may be used by an operator to position the sensor orientation during the robot teaching process. In addition, the center of the ellipse may be used to position the sensor in the depth direction.
As an aid to the operator, the desired ellipse may be digitally stored in the processor associated with the sensor and combined with the incoming camera signal. This results in a monitor display of the stored pattern and the teaching pattern. The operator then positions the sensor to match patterns.
It may also be possible to project an elliptical pattern which will appear, on the monitor, as a circle and may be easier to use during the teaching process.
This technique may also be used for focusing optical systems on a particular feature of a workpiece, for identifying and entering feature data as well as feature range location.
An alternate technique uses a single camera and two projectors. If the two projected patterns are identical then, in a manner similar to that previously described, the camera sees overlapping patterns when range and orientation are correct. The two projected patterns can be individually identified by turning one on and off or by making one dotted or discontinuous. In this manner the relative position in range, whether the objects are too close or too far apart, may be determined by the viewed pattern positions.
The two projected patterns can be different to aid alignment. If a cross and circular pattern are projected, then the relative location of the cross with respect to the circle, as seen by the camera, indicates in which direction, in or out, to move to get the desired standoff distance. The correct standoff is achieved when the cross is centered in the circle. Alternate projected patterns can be similarly used.
This technique may be applied to optically position one device with respect to another.